Description

• Cardiomyopathy encompasses a large group of diseases of the myocardium that commonly result in mechanical and/or electrical pump dysfunction. Prior classification schemes emphasized anatomic and functional features, which often led to confusion due to the heterogeneity and overlap between classes. In 2006, the AHA proposed a classification scheme that takes this into consideration and attempts to differentiate between myocardial diseases confined to the myocardium (primary) and those due to systemic disorders (secondary) (1). Specific causes of myocardial dysfunction due to other cardiovascular disorders are considered a third, separate category (1)

• Classification of cardiomyopathy:
  • Primary:
    • Genetic:
      • Hypertrophic (HCM)
      • Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D)
      • Left ventricular (LV) noncompaction (LVNC)
      • Glycogen storage (Danon type, PRKAG2)
      • Conduction defects
      • Mitochondrial myopathies
      • Ion channel disorders: Long QT syndrome, Brugada, short QT Syndrome, catecholaminergic ventricular tachycardia (CVPT), Asian SUNDS
    • Mixed:
      • Dilated (DCM) (genetic or nongenetic)
      • Restrictive
    • Acquired:
      • Myocarditis, stress cardiomyopathy, peripartum, tachycardia-induced, infants of type 1 diabetic mothers
  • Secondary (see list below)
  • Specific:
    • Ischemic
    • Valvular
    • Hypertensive
    • Congenital heart disease
• End-stage cardiomyopathy patients have stage D heart failure or severe symptoms at rest refractory to standard medical therapy.
• System(s) affected: Cardiovascular; Renal

Pediatric Considerations
Etiology: Idiopathic, viral, congenital heart disease, and familial

Pregnancy Considerations
May occur in women postpartum

Epidemiology

Predominant age: Ischemic cardiomyopathy is the most common etiology; predominantly in patients >50 years. Consider uncommon causes in young.

• 60,000 patients <65 die each year from end-stage heart disease.
• 35,000–70,000 people might benefit from cardiac transplant or chronic support.

Prevalence
Most rapidly growing form of heart disease

Risk Factors

• Hypertension
• Hyperlipidemia
• Obesity
• Diabetes mellitus
• Smoking
• Physical inactivity
• Excessive alcohol intake
• Dietary sodium
• Obstructive sleep apnea
• Chemotherapy

Genetics
Autosomal dominant HCM is the most common form of primary genetic cardiomyopathy (1:500 in the general population). Genetic causes of DCM are less common, acccounting for 1/3 cases, with mostly autosomal dominant inheritance. ARVC is also inherited in autosomal dominant fashion, in addition to LQTS and other ion-channel disorders.

General Prevention

Reduce salt and water intake; home BP and daily weight measurement

Etiology

The most frequent causes are in bold:

• Ischemic heart disease: Most common etiology; up to 66% of patients
• Hypertension
• Valvular heart disease
• Primary genetic causes
• Congenital heart disease
• Peripartum/Postpartum
• Endocrine:
  • Diabetes mellitus
  • Hyperthyroidism
  • Hypothyroidism
  • Hyperparathyroidism
  • Pheochromocytoma
  • Acromegaly
• Nutritional deficiencies:
  • Beriberi, pellagra, scurvy, selenium, carnitine, kwashiorkor
• Autoimmune/Collagen:
  • Systemic lupus erythematosus
  • Dermatomyositis
  • Rheumatoid arthritis
  • Scleroderma
  • Polyarteritis nodosa
• Infectious causes:
  • Viral (e.g., HIV, Coxsackie virus, adenovirus)
  • Bacterial and mycobacterial (e.g., Diphtheria, rheumatic fever)
  • Parasitic (e.g., Toxoplasmosis, Trypanosoma cruzi)
• Infiltrative:
  • Amyloidosis
  • Gaucher disease
  • Hurler disease
  • Hunter disease
  • Fabry disease
• Storage:
  • Hemochromatosis
  • Fabry disease
  • Glycogen storage disease (type II, Pompe)
  • Niemann-Pick disease
• Neuromuscular/Neurological:
  • Duchenne and Emery-Dreifuss muscular dystrophies
  • Friedreich's ataxia
  • Myotonic dystrophy
  • Neurofibromatosis
  • Tuberous sclerosis
• Toxic:
  • Alcohol
  • Drugs and chemotherapy: Anthracyclines, cyclophosphamide, Herceptin
  • Radiation
  • Heavy metal, chemical agents
• Inflammatory (granulomatous):
  • Sarcoidosis
• Idiopathic
• Endomyocardial:
  • Endomyocardial fibrosis
  • Hypereosinophilic syndrome (Loeffler's endocarditis)